Added GPU Acceleration in appropriate area

I've added a translateZ to shift the overlay and lightbox off the main layer on their own compositing layer, added a `3d perspective` (this helps minimize some browsers from janking momentarily on opacity changes) and set the backface to hidden (this will disable some of the GPU intensive stuff that `3d perspective` items have but telling it to only show the front face).

all of this should help to minimize the effects of layout thrashing (also known as jank).